(i) Field of the Invention
The present invention relates to a working micro-electrode with a reference electrode and a working micro-electrode with a reference electrode and a counter electrode. Each of the working micro-electrode with the reference and the working micro-electrode with the reference electrode and the counter electrode can be used as, for example, any one of all electrochemical detectors, environmental analysis sensors, pathologic inspection sensors, and probe electrodes which are for the detection of an organism, a food and the like, and which is severely required to be harmless and non-toxic. Furthermore, the present invention also relates to methods for preparing them.
(ii) Description of the Prior Art
An abbreviated rapid analysis using a sensor as a detecting means which has been promptly developed in recent years in many fields of an electrochemical determination has a very high selectivity and permits a high-sensitive measurement, and for this reason, this kind of abbreviated rapid analysis begins to be often used in the analysis and evaluation of clinical samples and environmental samples each containing a trace amount of a component to be determined and simultaneously many other kinds of compounds.
However, a working micro-electrode and a micro-sensor electrode have not been put into practice because of technical difficulty, except for a relatively large working electrode (diameter=about 10 mm) with a reference electrode, and a composite ion sensor with a reference electrode for measuring a hydrogen ion concentration and a metallic ion concentration which have been already practiced. Therefore, in the above-mentioned fields where measurement is made for a trace amount of a sample or in a micro-region, the employment of the thick reference electrode fairly reduces the merit of the working micro-electrode.
Lately, it has become very important to obtain biological information in vivo and in situ in a local site of an organism, for example, in a cell by the use of a sensor electrode capable of detecting such a specific material with a high sensitivity. For this purpose, it is required that the electrode is disposed in the vicinity of a target cell of the organism or thrust into the cell to give a physical, chemical or electrical irritation to the cell, so that a response material is released or a specific material chemically produced is selected to achieve its determination. Also for this purpose, it is fair to say that the assembly of the micro-electrode with the micro-reference electrode is a significant technique.
As such composite type measuring electrodes, a pH meter for determining hydrogen ions, an ion sensor for detecting inorganic ions such as sodium ions and the like, have been heretofore put into practice, as described above.
However, most of the composite electrodes cannot withstand a long-term use except for large composite electrodes (diameter=about 10 mm) such as the pH meter, the inorganic ion sensor and a metallic (mainly platinum) electrode for titration. That is, they have the drawback that a life is short. In particular, most of the composite electrodes in which a working electrode having a diameter of 1 mm or less is associated with a reference electrode and a counter electrode can scarcely withstand practical use.